Milos Raonic joined Novak Djokovic in the last four of the ATP World Tour Finals after knocking out rookie Dominic Thiem with a straight sets victory at The O2 Arena in London. The 25-year-old, with seven-time grand slam champion John McEnroe in his players' box, won 7-6 6-3 to march into the semi-finals for the first time, where he could play world number one Andy Murray.

Nothing could seperate the pair in a tightly contested first set, with neither player able to manufacturer a break point. Raonic then showed his class with an ace securing the subsequent tie-break 7-5 as Thiem's level dropped at the crucial moment.

Raonic claimed the first break of the match in the opening game of the second set and then took the second of two match points on the serve of the 23-year-old Thiem, who was unable to reproduce the stinging groundstrokes which had troubled his opponent at the outset. Murray, Kei Nishikori or Stanislas Wawrinka will represent the obstacle between Raonic and the final on Saturday [19 November], where he is likely to pose a real threat.

"I got fortunate at the end of the first set to hit three aces that helped me out a lot," he said. "I helped me in a lot of important moments today. I stuck with my weapons, I stuck with what I know how to do and I was fortunate to get through today."

The knock-out round came a stage early to the season-ending tour finals with Raonic and Thiem avoiding the mathematical equations; knowing victory by any means would be enough to join Djokovic in the last four. Both players had recorded identical results in their two round robin matches, losing to Djokovic and beating injury victim Gael Monfils.

A key theme of both player's campaign had been their dominating service game - and that very much continued during the opening exchanges of their all-or-nothing clash in London. Raonic was hammering down serves approaching 140mph, and Thiem was matching him for every stroke while his missile-like backhand proving too hot for his Canadian opponent to handle.

Neither player blinked despite the Austrian Thiem being taken to deuce as he served to stay in the set, resulting in an almost unavoidable tiebreaker. Raonic grabbed the first mini break but four errors in a row allowed Thiem to lead 4-2 at the changeover. But Raonic produce a four-point run of his own to tee up two set points, the second of which he took via his 11th ace of the match

No player had won from losing the first set on the ATP tour, with 16 victories, than Thiem but building on that record looked a thankless task when Raonic went ahead in the second set. He established the first break of the match as Thiem was unusually inaccurate on the backhand side.

Thiem did stem the flow when he saved two game points for a double break in his next service game, as Raonic threatened to get away from him. But he couldn't threaten the Raonic serve sufficiently to force his way back into the match and when Thiem dropped serve for a second time it allowed the Wimbledon runner-up to cruise into the knock-out stage.